Meandering pulmonary vein

Gender, Age

Female, 28

Diagnosis

Meandering pulmonary vein

History

Asymptomatic. Patient was undergoing work up for infertility.

Findings

Chest radiograph showed an abnormal tubular radiopacity in the para cardiac region of the right lung with mild volume loss of the right lung (Fig 1). The cardiac silhouette appeared normal. Scimitar syndrome was suspected based on the chest x-ray and contrast enhanced computed tomography scan of the thorax was done. On contrast enhanced CT (CECT) there was replacement of the normal right pulmonary veins by an abnormal single tortuous pulmonary vein with a meandering course through the right lung beginning in the right upper lobe and coursing posteriorly and medially and draining into the left atrium (Fig 2). The main pulmonary artery, right and left pulmonary arteries were found to be normal. No systemic collateral vessels were seen. In addition, there was absence of the right middle lobe bronchus, the horizontal and oblique fissures with a single fissure seen separating the apical segment of the right upper lobe from the rest of the right lung parenchyma suggesting pulmonary hypoplasia (Fig 3). Echocardiography of the patient was found to be normal.

Discussion

Meandering pulmonary vein also called pseudo-Scimitar syndrome or Scimitar variant is an extremely rare pulmonary venous anomaly which could be confused with the classical Scimitar syndrome which is a relatively more common condition with similar appearance of a linear opacity in para cardiac location on chest x-ray. Unlike the Scimitar syndrome where the abnormal pulmonary vein drains into the inferior vena cava, in pseudo-scimitar the pulmonary vein has an abnormal course but drains normally into the left atrium. The following case is an example of this condition.
The classical Scimitar syndrome consists of hypoplasia of the right lung, dextroposition of the heart, hypoplasia of the right pulmonary artery, an abnormal pulmonary vein draining into the inferior vena cava (IVC) and a systemic collateral supply to the lung. Several variants of the Scimitar syndrome have been described of which one rare variant includes a single tortuous scimitar like vein draining into the left atrium. The term “meandering pulmonary vein” was first used by Goodman et al to describe a single large right pulmonary vein which drained into the left atrium instead of the inferior vena cava as would be seen in a case of true scimitar vein]. The term Anomalous unilateral single pulmonary vein (AUSPV) is also used. Unlike the true scimitar syndrome, the drainage in case of AUSPV is orthotopic.
These are congenital anomalies of the pulmonary venous system in which there is partial anomalous pulmonary venous drainage without abnormal course in the lung. As these vessels drain into the left atrium, right to left shunting is not seen and hence the patients are usually asymptomatic, mostly detected incidentally. They do not require any intervention.
It has been hypothesized these anomalies occur during the primitive splanchnic capillary stage of development. Atresia of one of the pulmonary veins after the splanchnic circulation has separated but before the pulmonary segmentation has occurred might be the cause of AUSPV formation.
Several cases have been reported with associated anomalies in patients with a meandering pulmonary vein and hence one should be on the lookout for other findings while evaluating these cases which include dual drainage both to the IVC and left atrium, bilateral anomalous single pulmonary veins draining into the left atrium, hypoplasia of the right main pulmonary artery and mirror image lung, right lung and pulmonary artery hypoplasia with bilateral left sided bronchial configuration.
AUSPV or meandering pulmonary vein can mimic several other pathologies such as the true scimitar syndrome, pulmonary nodules, pulmonary arteriovenous malformations, pulmonary varices etc. It is important to distinguish between these pathologies and make the correct diagnosis as the management varies significantly. Although pulmonary angiography is the gold standard for the diagnosis of pulmonary venous anomalies non-invasive techniques like MDCT and magnetic reson

Pearls

Meandering pulmonary artery is a variant of the classical scimitar syndrome in which the pulmonary artery has an abnormal course but normal drainage into the left atrium. Since this condition generally does not require any intervention it is important to distinguish this entity from the classical scimitar syndrome in which the abnormal vessel drains into the inferior vena cava.